You can say that again!
I agree!
Hitting the books.
Studying hard.
It's raining cats and dogs.
It's raining hard.
In hot water.
In trouble.
I'm all ears.
I'm listening.
Don't "throw in the towel!"
Don't give up!
She is "catching some Z's."
She is sleeping.
Break a leg.
Good luck!
You're the "teacher's pet."
The teacher's favorite student.
He got up on the wrong side of the bed.
He's grouchy.
Hold your horses.
Wait.
It slipped my mind.
I forgot.
Don't let the cat out of the bag.
It means don't tell the secret or don't ruin the surprise.
The world is your oyster.
You can achieve anything.
Give it a shot.
Try it.
Multiplication is a "piece of cake."
It is not hard, it's easy!
You can't teach an old dog new tricks.
It's hard for old people to learn something new.
It costs an arm and a leg.
It's expensive.
He is feeling "under the weather."
He feels sick.
You're pulling my leg.
You're joking.
Let's pig out!
Eat a lot!
Hit the sack.
Go to sleep.